Our recent findings confirm that patients with active myofascial trigger points (MTrPs) have a significantly different biochemical profile (i.e., elevated levels of pro- inflammatory mediators, neuropeptides, cytokines, and catecholamines) within the local milieu of the MTrP compared to those without MTrPs or those with a latent (non-symptomatic) MTrP. These classes of substances are known to be associated with chronic pain states. Furthermore, we found significant differences in analyte levels at needle insertion between the trapezius and unaffected gastrocnemius in the Active group, suggesting that the vicinity of the active MTrP exhibits a unique biochemical milieu of substances associated with pain and inflammation. Additionally, gastrocnemius analyte levels were higher in the Active group than either the Latent or Normal groups. This further suggests that analyte abnormalities may not be limited to local areas of active MTrPs in the upper trapezius but may also be present at sites remote from the active MTrP. [unreadable] [unreadable] It is unclear how the symptoms and physical findings of MTrPs behave over time; they could improve, worsen or remain stable. It is suspected that the symptoms and physical findings of MTrPs will change over time, and these changes will correlate with biochemical analyte levels.[unreadable] [unreadable] The question that we would like to answer in this study is:[unreadable] [unreadable] What is the natural history of MTrPs with respect to pain, local physical findings, and its biochemical milieu (i.e., pro-inflammatory mediators, neuropeptides, cytokines, catecholamines, anti-inflammatory mediators, peripheral opioids and enzymes involved in muscle metabolism.)? [unreadable] [unreadable] We will select three groups of subjects based on the following characteristics 1, 2, and 3 below and follow them for 12 weeks. We will follow all subjects clinically with physical findings and a self-reported questionnaire. Half of the subjects of each group (Normal, Latent and Active) will undergo microdialysis sampling at standardized sites (GB-21 in the upper trapezius muscle and LV-7 in the medial gastrocnemius). The remaining half of the subjects will undergo all of the same evaluations except for microdialysis sampling.[unreadable] [unreadable] A goal of this study is to elucidate the pathophysiology of myofascial trigger points by following the natural history of clinical findings and the local biochemical milieu of the upper trapezius and medial gastrocnemius. Additionally, we would like to investigate whether changes in clinical findings are associated with changes in analyte levels. [unreadable] [unreadable] The acupuncture points GB-21 and LV-7 are selected specifically to standardize the locations of a sampling point in three distinct groups: [unreadable] [unreadable] 1) Normal - healthy subjects without pain and who have no MTrPs identified by palpation[unreadable] bilaterally in GB-21, and who do not have MTrPs identified by palpation bilaterally in LV-7;[unreadable] [unreadable] 2) Latent - healthy subjects without pain in whom latent MTrPs are identified by palpation [unreadable] in GB-21 in one of the upper trapezius muscles, and who do not have MTrPs identified by [unreadable] palpation bilaterally in LV-7; and[unreadable] [unreadable] 3) Active - healthy subjects complaining of neck pain of less than 3 months duration with active [unreadable] MTrPs identified by palpation in GB-21 in one of the upper trapezius muscles, and who do not[unreadable] have MTrPs identified by palpation bilaterally in LV-7.